Aromatic dicarboxylic acid polyamide having acid value greater than 35

ABSTRACT

Polyamide resins are prepared from aromatic dicarboxylic acids and which are substantially free of dimeric or higher polymeric fat acids. The resins generally have improved alkaline water solubility or dispersibility having substantially lower solution viscosities than prior polyamide resins. The harder resins with their water solubility find particular utility as ink binders. The softer resins find utility as a film layer bonding two flexible substrates.

FIELD OF THE INVENTION

This invention relates to polyamide resins prepared from aromaticdicarboxylic acids and which are substantially free of dimeric or higherpolymeric fat acids. The resins generally have improved alkaline watersolubility or dispersibility having substantially lower solutionviscosities than prior polyamide resins. The harder resins with theirwater solubility find particular utility as ink binders. The softerresins find utility as a film layer bonding two flexible substrates.

BACKGROUND OF THE INVENTION

Flexographic inks are solvent based inks applied by rollers or pads toflexible sheets or rolls of plastic foil and paper. The practicalaspects of the use of these ink resins, and inks derived therefrom,require that the polyamide resin be soluble in alcoholic solvents andsuch solubility be obtained without sacrificing toughness, adhesion andgloss.

Environmental concern over the amounts of volatile organic solvents inthe atmosphere has led to a desire to use aqueous solutions that haveless volatile organic solvents contained therein. In order toaccommodate the reduced levels of volatile organic solvents, thepolyamide resins used as binders should have increased water solubilityand yet retain the other desirable properties of polyamide resins suchas those based on the polymeric fatty acids.

U.S. Pat. Nos. 3,253,940 and 3,224,893 illustrate the polyamide resinsof polymeric fatty acids used in the past in formulations utilizingalcoholic solvents particularly ethanol in which varnishes of thepolyamides in alcohol solvents were on the order of 35% by weightnonvolatile solids.

The foregoing patents provided resins which could be employed with theusual alcoholic solvents. However, as environmental solutions weresought, efforts were made to reduce emissions such as those from thevolatile alcohol solvents. One means of reducing the emission was toprovide water-reducible polymeric fatty acid polyamides as illustratedin U.S. Pat. No. 3,776,865. As disclosed therein, this was achieved byacid termination of the polymeric fatty acid polyamides employing anacid component of the polymeric fatty acid and another codicarboxylicacid and an amine component comprising isophorone diamine alone or inadmixture with conventional diamines such as the alkylene diamines i.e.,ethylene diamine. Acid termination was achieved by employing about 50-75amine equivalents per 100 carboxyl equivalents. Varnishes of theseresins in an alcohol solvent such as n-propanol on the order of about40% non-volatile solids are disclosed.

Another U.S. patent, U.S. Pat. No. Re. 28,533 dealing with polymericfatty acid polyamides employing lower aliphatic mono-basic acids such asacetic and propionic with certain amine combinations disclosed a fewsolubilities in ethanol up to 60% though many were 50% or below.

As environmental standards have become more and more stringent, efforthave continued to provide resins which comply with such standards. Highsolids varnishes on the order of 55-60%, and preferably above 60%, whichare formulated into pigmented inks will meet the solvent emissionsstandards desired in order to reduce solvent emissions. U.S. Pat. No.4,508,868 discloses polyamides prepared from polymeric fatty acids anddiamines which include in the acid component an unsaturated fatty acidmonomer and which employ relative amine and carboxyl amounts so as toprovide an acid terminated product having an acid value in the range of8-20 and preferably in the range of 10-15. Such products could beemployed in alcoholic ink varnishes at levels of 60% solids or higher.

However, the polyamide resins from polymeric fatty acids, whileproviding acceptable properties in most instances, do not possess thedesired water solubility or dispersibility when employed in inks orvarnishes. Accordingly attempts have been made to improve the hardnessand water solubility products which contain even lower volatile organicsolvents. Commonly assigned co-pending application Ser. No. 701,903filed Feb. 15, 1985 by Whyzmuzis, et al, now abandoned, was an attemptto overcome the deficiencies of the polymeric fatty acid polyamideresins. This patent application discloses polyamides which aresubstantially free from polymeric fatty acids which have improved watersolubility in their use with flexographic or gravure ink binders. Whilesuch resins provided generally acceptable products, there was still roomfor improvement in the hardness or non-tacky properties of the resins.

SUMMARY OF THE INVENTION

It has now been found that further improved polyamide resinssubstantially free from polymeric fatty acids and useful asflexographic/gravure ink binders are provided by employing an aromaticdicarboxylic acid in the acid component. The use of the aromaticdicarboxylic acids provide resins having improved hardness or non-tackyproperties while retaining the advantageous properties of the earlierresins such as those of U.S. Pat. No. 4,508,868 or U.S. patentapplication Ser. No. 701,903, noted above. Thus, the present inventionprovides resin compositions formed from a mixture of X equivalentpercent of an acid component and Z equivalent percent of an aminecomponent wherein the acid component is comprised of an aromaticdicarboxylic acid alone or in a mixture with an aliphatic dicarboxylicacid having from 2-25 carbon atoms, and said amine component iscomprised of a diamine alone, a monoalkanol amine alone or mixtures ofdiamine and monoalkanol amine and the ratio of Z:X is less than 1 toprovide a polyamide having an acid value greater than about 35. Thepreferred polyamides are those wherein the ratio of Z:X is less thanabout 0.9, more preferably ranges from 0.50 to about 0.85, and mostpreferably from about 0.65 to about 0.85.

In addition to providing the foregoing polyamide resins, this inventionalso provides binder compositions such as flexographic/gravure inkcompositions containing such resins and aqueous solvents and inkpigments. In addition to the use in flexographic/gravure inkcompositions, the polyamide resins of this invention also find utilityin coating compositions where harder, non-tacky coatings are desiredparticularly where it is desirable to apply such coatings from aqueoussolvent solutions having low solution viscosities, with or withoutpigments. Further, the softer resins may be employed when it isdesirable to bond two flexible substrates where adhesion to each isdesirable.

DETAILED DESCRIPTION OF THE INVENTION

The polyamide resins of the present invention are prepared bypolymerizing a mixture of the amine component and the acid component.The resins are acid terminated resins in that an excess of dicarboxylicacids are used in relation to the amine component reactants. If amonobasic acid is desired to be used as a chain-stopper, such should beemployed in limited, or very small amounts (less than 10, and preferablyless than 5 equivalent percent), as their presence can adversely affectthe properties of the polyamide resin. The ratio of equivalents of theamine component to the equivalents of acid component is less than 1,preferably less than about 0.9, more preferably ranges from 0.50 toabout 0.85, and most preferably about 0.65 to 0.85. In considering theequivalents of the amine component, it is necessary to take intoconsideration the hydroxyl group of the alkanolamine which is alsoreactive with the carboxyl groups of the acid component and whichresults in a polyester-amide, i.e. a polyamide also containing estergroups. Accordingly, where reference is made to the equivalents of theamine component, it is understood that both the hydroxyl and amineequivalents of the amine component are considered.

As indicated earlier in the polyamide resins of this invention, anaromatic dicarboxylic acid is employed either alone or in admixture withcopolymerizing aliphatic dicarboxylic acids. In general, the aromaticdicarboxylic acid which are employed will contain from 8-16 carbonatoms. Such acids include phthalic, isophthalic, and terephthalic, anddiphenic and naphtalene dicarboxylic acids, isophthalic and terephthalicbeing the preferred acids.

The aliphatic dicarboxylic acids which may be employed along with thearomatic diacid are those having from 2-25 carbon atoms with thelonger-chain acids, i.e., from 13 and above, with the 16-21 carbon atomacids being the most desirable. The dicarboxylic acids include not onlythe straight-chain aliphatic acids, but also include those havingbranched alkyl chains and alicyclic structures in the molecule as well.Accordingly, the dicarboxylic acids include the usual shorter-chainacids beginning with ethanedioic and the usual aliphatic dicarboxylicacids such as azelaic, adipic and sebacic acid. The class also includeslonger-chain dicarboxylic acids such as heptadecane dicarboxylic acid (aC₁₉ acid) and acids obtained by the Diels-Alder reaction products ofacrylic acid with a fatty acid having conjugated ethylenic unsaturationsuch as 2-n-hexyl-5-(7-carboxyl-n-heptyl)-cyclohex-3-ene (a C₂₁ diacid)carboxylic acid which is available from Westvaco, Charleston Heights, SCas Westvaco diacid. Heptadecane dicarboxylic acids are well known andprepared via the known process of carboxylation of oleic acid.References to these acids are made in U.S. Pat. No. 3,781,234 which inturn makes reference to German Pat. No. 1,006,849 for the preparation ofthe 1,8- or 1,9-heptadecane dicarboxylic acid.

As indicated, the aromatic dicarboxylic acid is employed alone or in amixture with the aliphatic dicarboxylic acids. Where employed, thealiphatic dicarboxylic acid may be employed in an amount up to about 50equivalent percent of the acid component, or a ratio of equivalents ofaromatic to aliphatic dicarboxylic acid of 1:1. Stated another way, theacid component may accordingly be comprised of (a) 50-100 equivalentpercent of the aromatic dicarboxylic acid and (b) 0-50 equivalentpercent of the aliphatic dicarboxylic acid.

As earlier noted, the polyamides of this invention are prepared frommixtures that are substantially free of polymeric fatty acids. Thesepolymeric fatty acids, which can be characterized as long-chainpolybasic acids, are described in U.S. Pat. No. 3,776,865 and U.S. Pat.No. 3,157,681. These polymeric fatty acids are derived by polymerizingunsaturated fatty acids. If necesary to modify the resins of the presentinvention, such polymeric fatty acids may be used in very small amounts,i.e. up to about 5 equivalent percent. Preferably no polymeric fat acidshould be employed.

The diamines used to form the polyamide resins of this invention may bearomatic or aliphatic, cyclic and heterocyclic. Preferably, the aminecomponent contains at least one aliphatic diamine having 2-25 aliphaticcarbon atoms or an akanolamine such as discussed below. The preferreddiamines can be divided into various preferred groups, mixtures of whichmay be employed. In the aromatic or heterocyclic group amines such aspiperazine and xylylene diamine may be employed. In the cycloaliphaticgroup, cyclic aliphatic diamines having from 8-12 aliphatic carbonatoms, e.g., isophorone diamine may be employed. Another preferred groupis comprised of short-chain alkylene diamines which can be representedby the formula: H₂ N--R--NH₂, wherein R is an alkylene radical havingfrom 2-8 carbon atoms. R may be branched or straight-chain, thestraight-chain radicals being preferred. Specific examples ofshort-chain alkylene diamines are ethylene diamine, diaminopropane,diaminobutane, and hexamethylene diamine. Another group is the shortchain polyether diamines which are commercially available, which may bedefined by the formula:

    HN.sub.2 --R'--(O--R').sub.x --O--R'--NH.sub.2

where R' is an alkylene group containing 2-6 carbon atoms, preferably anethylene or isopropylene group and x is an integer of 0-5, preferably 1or 2, such that an average molecular weight not more than about 400 andpreferably less than about 250. Commercially available polyetherdiamines are Jeffamine D-230 and 400 described by the supplier aspolyoxypropylene diamine.

The monoalkanolamines which may be employed alone or in admixture withthe aromatic, aliphatic or heterocyclic diamines in this invention arethose containing 2-6 carbon atoms, straight or branched-chain, which maybe represented by the formula: OH--R"--NH₂ wherein R" is an alkyleneradical having from 2-6 carbon atoms. Specific examples of short-chainmonoalkanolamines are ethanolamine, propanolamine, and butanolamine,with the ethanol and propanolamine products being preferred.

The resins are prepared from mixtures of a dicarboxylic acid componentand an amine component by known methods for the polymerization ofdiacids and diamines to form polyamides. In general, a mixture of thediacid component and the amine component is heated to a temperature ofbetween 100°-250° C. in a vessel equipped for the removal of theby-product water formed in the amidification reaction; e.g., a vesselfitted with a distillation column and condenser so as to remove waterfrom the reaction zone.

Typically, the reaction mixture will be heated at lower temperaturesinitially to avoid any volatilization and loss of any reactant which maybe employed, after which the temperature is raised to a higher reactiontemperature. Thus, it is common to heat at a temperature of about 140°C. for about 1 hour followed by raising the temperature to about210°-250° C. and reacting for 1.0-3.0 hours, preferably with the lasthour under vacuum.

The degree of polymerization of the mixture is controlled, along with achoice of ratio of amine:acid, to provide a polyamide having a high acidvalue. The acid value of the polyamide should be greater than about 35,more preferably greater than 50, i.e. between 50 to about 250, dependenton the particular amine and acid formulation.

The polyamide resins of this invention form the binder compositions ofthis invention when dissolved in an aqueous solvent containing ammoniaor an organic amine. The resin is added to the solvent in an amount ofabout 30-40% resin solids based on the weight of the solvent. Examplesof suitable organic amines include primary, secondary, and tertiaryamines which can act as a base to salt the acid terminated polyamides.Particularly preferred organic amines are the dialkyl aminoalkanols suchas 2-(N,N-dimethylamino)ethanol and 2-(N,N-diethylamino)ethanol.

The organic amine is present in the aqueous solution in an amountsufficient to solubilize the chosen polyamide resin. In general, theorganic amine will be present in the aqueous solution in an amountsufficient to theoretically neutralize the acid groups of the polyamide,i.e., the amount of organic amine is stoichiometrically equivalent to orgreater than the acid value of the polyamide. For example, a 7.4%solution of dimethylaminoethanol is stoichiometrically equivalent to apolyamide resin having an acid value of about 70 used at a level ofabout 40% resin solids. A large excess of organic amine should beavoided because retention of the organic amine in the cured binder mayadversely affect the water resistance of the binder.

These binders are particulaly useful in flexographic/gravure inkcompositions. The resins may also be useful in other coatingcompositions where harder, non-tacky products are desired or in thecases of softer, somewhat tacky products, in bonding two flexiblesubstrates where adhesion to each substrate is desirable. Where employedin ink compositions, the inks are prepared by dispersing aflexographic/gravure ink pigment in the binder compositions of theinvention.

The invention can be further illustrated by the following nonlimitingexamples in which all parts and percentages are by weight, unlessotherwise noted. In the examples there are shown polyamides of thepresent invention generally denoted by arabic numbers and comparativeexamples are generally denoted by a letter. Further, in the examples theterms, abbreviations and symbols have the following meanings:

IPA: Isophthalic Acid (1,3)

PA: Propionic Acid

EDA: Ethylene Diamine

D-230: Jeffamine D-230--Polypropylene Diamine available from TexacoChemical Company having molecular weight about 230

D-400: Jeffamine D400--Polypropylene Diamine having molecular weight ofabout 400

C₂₁ : Westvaco C₂₁Diacid--2-m-hexyl-5-(7-carboxyl-n-heptyl)-cyclohexo-3-ene carboxylicacid

MEA: Monoethanolamine

HMDA: Hexamethylene Diamine

T.Av.: Theoretical Acid Value

Act.Av.: Actual Acid Value

Am.V.: Amine Value

OH V.: Hydroxyl value

SP°C.: Softening Point °c. (Ball & Ring)

P.S.: Physical State

Sol.: Solubility

C3M-30: Solvent Composition 75.2/15.9/5.8/3.1-H₂O/n-proponol/Dimethylethanol Amine/NH₄ OH

P.E.Wet: 30% Solid Varnish (Resin plus Solvent) wets out polyethylene

H₂ O Tack: Resin alone develops tack with H₂ O immersion

H₂ O Resist: Films of dried varnish on polyethylene subjected to 100 H₂O rubs with finger after 30 minute exposure

Disp.: Stable dispersion

Typical Resin Preparation

The resins described in the examples summarized in the following Table Iwere prepared by charging the acid and amine reactants shown in Table Ito a reactor along with about 1% of an 85% solution of phosphoric acidas a catalyst. The reaction mixture was heated to 210° to 250° C. andheld for 1 to 2.5 hours at that temperature. The resulting resin has theproperties as shown in Table II, Comparative Example A, which has aGardner Holdt solution viscosity of H-I, illustrates a composition suchas found in application Ser. No. 701,903.

Examples 1-17 illustrate resins of this invention which are soluble inaqueous solutions and which find utility in ink varnishes. Each of thesesolutions are very low solution viscosity products having a solutionviscosity on the order of water alone, i.e. Gardner Holdt of AA₁.Examples 16 and 17 which are tacky are resins which could be applied outof aqueous solutions but which may be better suited for applicationwhere their tackiness is advantageous, i.e. in bonding two flexiblesubstrates where adhesion to each substrate is desired.

                                      TABLE I                                     __________________________________________________________________________    Equivalents of Reactants                                                      Example                                                                             IPA C.sub.21                                                                          PA EDA MEA HMDA D-230                                                                             D-400                                       __________________________________________________________________________    A     --  75  25 81  --  --   --  --                                          1     100 --  -- 41.7                                                                              41.6                                                                              --   --  --                                          2     100 --  -- --  83.3                                                                              --   --  --                                          3     100 --  -- --  91.6                                                                              --   --  --                                          4      75 25  -- 77  --  --   --  --                                          5      65 35  -- 74.5                                                                              --  --   --  --                                          6      50 50  -- 70.7                                                                              --  --   --  --                                          7      75 25  -- --  77  --   --  --                                          8       87.5                                                                              12.5                                                                            -- --  80.2                                                                              --   --  --                                          9     100 --  -- --  61.8                                                                              20.6 --  --                                          10    100 --  -- 44.2                                                                              --  --   --  29.5                                        11    100 --  -- 51.5                                                                              --  --   --  34.3                                        12    100 --  -- --  --  --   70.7                                                                              --                                          13    100 --  -- --  --  --   88.5                                                                              --                                          14    100 --  -- 35.8                                                                              --  --   --  35.7                                        15    100 --  -- 42.3                                                                              --  --   --  42.3                                        16    100 --  -- 16.7                                                                              --  --   --  50.1                                        17    100 --  -- 20.4                                                                              --  --   --  61.0                                        __________________________________________________________________________

The physical properties of the resulting resin and evaluation of theresin, particularly in varnish solutons, for suitability as an ink resincan be seen from the following Table II.

                                      TABLE II                                    __________________________________________________________________________    Exam-                        Sol  PE H.sub.2 O                                                                        H.sub.2 O                             ple T.Av.                                                                             Act.Av.                                                                            Am.V                                                                              OHV SP °C.                                                                     P.S.                                                                              C3M-30                                                                             Wet                                                                              Tack                                                                             Resist                                __________________________________________________________________________    A   50  52   --  --   91 S1  H-I  yes                                                                              no OK                                    1   100 200.0                                                                              29.4                                                                              55.6                                                                              169 Hard                                                                              Disp.                                                                              no no --                                    2   100 182.3                                                                              19.7                                                                              5   154 Brittle                                                                           yes  no no --                                    3   50  138.4                                                                              20.4                                                                               6.2                                                                              157 Brittle                                                                           Disp.                                                                              no no --                                    4   100 118.1                                                                              14.0                                                                              --  142 Brittle                                                                           Disp.                                                                              yes                                                                              no OK                                    5   100 124.6                                                                              10.3                                                                              --  130 Brittle                                                                           Disp.                                                                              yes                                                                              no OK                                    6   100 118.0                                                                              11.0                                                                              --  115 Brittle                                                                           yes  yes                                                                              no OK                                    7   100 151.8                                                                               8.4                                                                              18.6                                                                              111 Brittle                                                                           yes  yes                                                                              no OK                                    8   100 162.9                                                                              11.3                                                                              20.6                                                                              128 Brittle                                                                           yes  yes                                                                              no OK                                    9   100 186.5                                                                              22.5                                                                              43.6                                                                              148 Hard                                                                              yes  no no --                                    10  100 108.8                                                                              10.3                                                                              --  111 Hard                                                                              Disp.                                                                              no yes                                                                              --                                    11  50  64.4 10.7                                                                              --  115 Hard                                                                              Disp.                                                                              no yes                                                                              --                                    12  100 105.3    --  103 Hard                                                                              Border                                                                             no S1 yes                                   13  38.2                                                                              42.9     --  108 Hard                                                                              Border                                                                             no S1 yes                                   14  100 112.5    --   97 S1  yes  no yes                                      15  50  60.1     --   96 S1  yes  yes                                                                              yes                                                                              Acpt                                  16  100 75.5  5.6                                                                              --  --  Tacky                                                                             yes  yes                                                                              yes                                                                              Mod.                                  17  50  50.7  4.3                                                                              --  --  Tacky                                                                             yes  yes                                                                              yes                                                                              Mod.                                  __________________________________________________________________________

Examples 1-17 summarized in Tables I and II illustrate compositionswhich have low solution viscosity in aqueous solutions. Examples 1-13are particularly desirable for ink varnishes for flexographic andgravure inks providing hard resins. Examples 14 and 15 while stillhaving slight tack are also useful for ink applications and compared toExample A have improved low solution viscosity.

Another series of resins were prepared and illustrate isophthalic acidbased polyamides having a range of properties of from very hard (thoughnot soluble in aqueous alkaline solutions) to semi-solid, semi-liquid orliquid products which find utility in other areas requiring watersolubility other than inks or ink varnishes. Such other resins canprovide coatings either 100% solids type or formed from the solventsystem where such can be tolerated. The compositions and propertiesthereof can be seen from the following Tables III and IV.

                  TABLE III                                                       ______________________________________                                        Equivalents of Reactants                                                      Example  IPA       C.sub.21                                                                             PA     EDA   D-400                                  ______________________________________                                        18        50*      25     25     78.8  --                                     19       100       --     --     83.3  --                                     20       100       --     --     57.8  19.2                                   21        75       --     25     58.0  19.3                                   22       100       --     --     --    70.7                                   ______________________________________                                         *IPA added in two stages                                                 

                  TABLE IV                                                        ______________________________________                                                Examples                                                                      18    19        20     21     22                                      ______________________________________                                        T.Av.             100       100  100    100                                   Act.Av.   154.0   84.0      151  --     63.7                                  Am.V.     10.3    22.5      --   --      1.7                                  OHV       --      --             --     --                                    SP °C.                                                                           77      192       129   80    --                                    P.S.      Sint.   V. Hard   Hard S. Liq.                                                                              Liq.                                  Sol. - C3M-30                                                                           no      no        no   --     yes                                   P.E. Wet  --      --        --   --     yes                                   H.sub.2 O Tack                                                                          no      no        mod. --     yes                                   H.sub.2 O Resist                                                                        --      --        --   --     no                                    ______________________________________                                    

EXAMPLE 23

Example 8 was repeated except that the time of reaction at 210° C. was3.5 hours with the last hour being under vacuum (10 mm). Operation undervacuum results in a lowering of the hydroxyl value with other propertiesbeing substantially the same. These can be seen from Table V below, inwhich the values for Example 8 are included for comparison.

    ______________________________________                                                      Example                                                                       23     8                                                        ______________________________________                                        SP °C.   135      128                                                  T.Av.           100      100                                                  Act.Av.           151.3    162.9                                              Am.V.             12.2     11.3                                               OH.V            5.0 ± 1.5                                                                             20.6                                               Sol. C3M-30     yes      yes                                                  PE Wet          yes      yes                                                  ______________________________________                                    

We claim:
 1. A polyamide resin formed from a mixture comprising:Xequivalent percent of an acid component substantially free from apolymeric fat acid comprised of an aromatic dicarboxylic acid and Zequivalent percent of an amine component wherein the ratio of Z to X isless than 1 to provide an acid value greater than 35 and wherein saidacid amine component is comprised of an amine selected from the groupconsisting of a monoalkanolamine and mixtures thereof with a diamine. 2.A polyamide as defined in claim 1 wherein said ratio of z to x is fromabout 0.50 to about 0.85.
 3. A polyamide as defined in claim 1 whereinsaid acid component is comprised of 50-100 equivalent percent of saidaromatic dicarboxylic acid and 0-50 equivalent percent of an aliphaticdicarboxylic acid having from 2-25 carbon atoms.
 4. A polyamide asdefined in claim 3 wherein said aliphatic dicarboxylic acid has from16-21 carbon atoms.
 5. A polyamide as defined in claim 4 wherein saidaliphatic dicarboxylic acid is heptadecanedicarboxylic acid.
 6. Apolyamide as defined in claim 4 wherein said aliphatic dicarboxylic acidis 2-n-hexyl-5-(7-carboxyl-n-heptyl)cyclohex-3-ene carboxylic acid.
 7. Apolyamide as defined in claim 3 wherein said aromatic dicarboxylic acidis isophthalic acid.
 8. A polyamide as defined in claim 1 wherein saiddiamine is an aliphatic diamine having from 2-25 carbon atoms.
 9. Apolyamide as defined in claim 8 wherein said diamine is an alkylenediamine in which the alkylene group contains from 2-8 carbon atoms. 10.A polyamide as defined in claim 8 wherein said diamine is ethylenediamine.
 11. A polyamide as defined in claim 8 wherein said diamine ishexamethylene diamine.
 12. A polyamide as defined in claim 8 whereinsaid diamine is a polyether diamine having an average molecular weightnot more than about
 400. 13. A polyamide as defined in claim 12 whereinsaid polyether diamine has a molecular weight below
 250. 14. A polyamideas defined in claim 1 wherein said monoalkanolamine contains from 2-6carbon atoms.
 15. A polyamide as defined in claim 14 wherein saidalkanolamine is ethanolamine.
 16. A binder composition which comprises apolyamide resin of claim 1 and an aqueous solvent containing ammonia andan organic amine.